1. Field of the Invention
The present invention relates to an objective revolver to be used in an optical apparatus such as a microscope, and is more particularly concerned with a scheme for arranging a motor for driving the revolver.
2. Related Background Art
There has been known a microscope provided with an objective revolver which is electrically driven to automatically exchange objective lenses.
Generally, as shown in FIG. 7, such an objective revolver 100 has a plurality of different objective lenses 101 and is attached to an arm 200.
The objective revolver 100 comprises, as shown in FIG. 8, a fixed member 110 to be fixed to a microscope, a rotating member 120 which is rotatably set to the fixed member 110 and a motor 130 for rotating said rotating member 120.
The fixed member 110 is fixed to the arm 200 (see FIG. 7) of the microscope by means of a round dovetail member 111, and a through hole serving as a part of the optical path of the microscope is formed through said round dovetail member 111.
The fixed member 110 revolvably supports the rotating member 120 with a group of steel balls 121, another group of steel balls 122 and a fixed shaft member 123. The rotating member 120 has a plurality of fitting holes 124 each fitting an objective lens 101, and a gear ring 126 around which a ringed external gear 125 is formed.
The motor 130 is fixed to the fixed member 110 by an L-shaped metal stopper 131. A bevel gear 133 is fixedly set around a rotation shaft member 132 of the motor 130. The bevel gear 133 is engaged with another bevel gear 134, which is fixed to an end of a rotation shaft member 135. Around the other end of the rotation shaft member 135, a gear 136 is formed, which is engaged with the external gear 125 of the gear ring 126.
The objective revolver 100 also has a cover 112 for preventing the rubbish caused by the engagement of the gears from falling down. The cover 112 is fixed to the fixed member 110 so as to cover the external gear 125 and the gear 136 and the engagement of the external gear 125 with the gear 136.
The objective revolver 100 rotates the motor 130 according to the directions from a switch (not shown) in order to transmit torque via the plurality of gears 133, 134, 136 and 125 to the rotating member 120, thereby exchanging the objective lenses to be positioned on the optical path including the optical axis 0.
In this conventional objective revolver, however, the motor 130 and the group of gears 133, 134, 136 and 125 for transmitting torque of the motor 130 are arranged outwards from the rotating member 120. Accordingly the arm 200 should have an inner space to contain the motor and the gears, which makes the strength of the arm 200 insufficient. Therefore, when a heavy lens barrel and/or other attachments (such as a photographing device) are mounted on the arm 200, the arm 200 becomes rickety and deflects and the optical axis deviates so that the image is blurred.